1. Field of the Invention
The present invention relates to a refrigerant pipe unit interconnecting an indoor unit and an outdoor unit of a room air-conditioner for circulation of a refrigerant through the room air-conditioner.
2. Description of the Related Art
Room air-conditioners functioning to keep the temperature of the air in rooms at about 18 to 25.degree. C. throughout the year are widely used.
As diagrammatically shown in FIG. 18, the conventional room air-conditioner 200 generally comprises an indoor unit 201, an outdoor unit 202, and two refrigerant pipes 203, 204 interconnecting the indoor and outdoor units 201, 202 for circulation of a refrigerant through the room air-conditioner. In the outdoor unit 202, a compressor 205 compresses the vaporous refrigerant to a higher pressure and passes it to an outdoor heat exchanger 206 where the vaporous refrigerant is condensed, giving off heat Q1 to the atmosphere. The liquid refrigerant is fed through to the refrigerant pipe 203 to an expansion valve 207 in the indoor unit 201. The expansion valve 201 expands the liquid refrigerant to a lower pressure and passes it to an indoor heat exchanger 208 where the liquid refrigerant is evaporated, absorbing heat Q2 from the surroundings. Thus, the temperature inside the room goes down. The vaporous refrigerant returns through the refrigerant pipe 204 to the compressor 205. The foregoing circulation of the refrigerant makes the room air-conditioner 200 serve as a cooling system.
Reversing the refrigerant circulating direction makes the room air-conditioner serve as a heat pump heating system, in which the refrigerant absorbs heat from the atmosphere at the outdoor heat exchanger and subsequently gives off this heat to the inside of the room at the indoor heat exchanger.
As generally known, the refrigerant pipes 203, 204 are laid through a piping hole 212 formed in a wall 211 of the building. After the piping work completes a clearance between the refrigerant pipes 203, 204 and the piping hole 212 is closed by a putty or a like sealing material 213 to protect the building against weather.
From the sealing point of view, the piping hole 212 in the building wall 211 is preferably as small as possible. But, a larger piping hole is convenient for the piping work. Heretofore, three diameters (65 mm, 75 mm and 85 mm) have been standardized for the piping hole 212. These standard piping diameters are selected depending on the capacity or power of a room air-conditioner in which the refrigerant pipes 203, 204 are used. For example, a 65-mm-diameter piping hole is chosen for home-use room air-conditioners, and an 85-mm-diameter piping hole is chosen for business-use room air-conditioners.
The present inventor has proposed a conventional room air-conditioner disclosed in Japanese Patent Laid-open Publication No. HEI 10-89815, entitled "Heat Exchanger and Method of Replenishing Refrigerant to the Same". The proposed room air-conditioner includes four valves provided at respective refrigerant inlets and outlets of indoor and outdoor units. When the air-conditioner is to be disassembled for moving or transportation, these four valves are closed, and after that the indoor unit, the refrigerant pipes and the outdoor unit are separated. A great part of the refrigerant is trapped inside the indoor and outdoor units. But, a small part of the refrigerant is emitted to the atmosphere when the refrigerant pipes are detached from the indoor and outdoor units. When the room air-conditioner is re-assembled at a new installation site, the refrigerant pipes are attached to the indoor and outdoor units. While all the valves are kept in the fully closed state, the refrigerant pipes are evacuated, then replenished with the refrigerant. Subsequently, all the valves are opened, thus placing the room air-conditioner in the operable condition.
Because the great part of the refrigerant, which is trapped within the indoor and outdoor units, can be used again, environmental contamination caused by emission of the refrigerant is reduced to the minimum.
However, as a demand for environmental preservation of the earth has increased year by year, emission of the refrigerant from the refrigerant pipes 203, 204 may also be rendered impermissible even though the emission quantity is small.
In addition, a prolonged use of the room air-conditioner may cause leakage of the refrigerant to the atmosphere, requiring replenishment of the refrigerant. This leakage also causes environmental disruption.
In recent years, a mixture of plural sorts of alternate Freon (a trademark for fluorocarbons) has been used as a refrigerant for room air-conditioners. Use of this type of refrigerant makes the replenishment substantially impossible because identification of leaked constituents is substantially impossible. Accordingly, when leakage of the refrigerant occurs, the alternate Freon mixture left in the room air-conditioner is fully removed, then a new alternate Freon mixture is filled in the room air-conditioner.
Under these circumstances, a technique which is capable of sealing the refrigerant inside the refrigerant pipes is required. The standard piping holes are sized to allow passage of two refrigerant pipes, but they do not allow passage of any conventional valve provided at an end of each refrigerant pipe.
In many cases, the refrigerant pipes are connected by the so-called flared type joining system. In this joining system, an end of a deoxidized copper pipe is inserted in a flare nut, then flared like a bell. The flared pipe end is subsequently forced against a chamfered front end of a nipple by tightly fastening the flared nut to the nipple. Because of the metal-to-metal contact, a joint formed between the refrigerant pipe and the nipple is liable to gradually allow leakage of the refrigerant due to a working error or vibrations. Additionally, since the diameter of the refrigerant pipes specified by Japanese Industrial Standards (JIS) is 8A or 10A (corresponding to a nominal diameter of 8 mm or 10 mm), a screwed pipe fitting is used for joining such small diameter pipes. The screwed pipe fitting is compact but it is insufficient to provide a reliable seal against leakage because the refrigerant can flow along threaded grooves. The screwed pipe fitting is susceptible to cracking at the bottom of the threaded grooves.